The Zapruder Film

The Zapruder Film was taken by dressmaker Abraham Zapruder as the assassination took place and is a key piece of evidence, providing a timing of the assassination. For example, the speed of the car can be determined by measuring it's position against a fixed object in the background. Also, the spacing of the shots can be determined by measuring the number of frames between the reactions of the victims (JFK, Gov. Connally).

For an exhaustive analysis of what information can be gleaned from the film, read the book Six Seconds in Dallas by Josiah Thompson.

Here is an interesting digitized composite version of the Zapruder Film that that appears to show each frame in sequence while showing information on nearby frames frozen in place in an effort to provide a broader context of the event.